Sexual Selection

2 types of selection: 1. Intrasexual Selection: Members of 1 sex COMPETE with each other for ACCESS to the other SEX. 2. Intersexual Selection: Females and Males CHOOSE partners with the most ATTRACTIVE attributes.

Intrasexual Selection: Competition

Intrasexual Selection: Competition

Intrasexual Selection 1. Competition: Leads to differences in reproductive SUCCESS. Charles DARWIN: Whoever SURVIVES will REPRODUCE. In most species, MALES compete for FEMALES

Intrasexual Selection 2. Why is there a difference between sexes? Different type and NUMBER of GAMETES (sperm/egg) produced by males and females

Intrasexual Selection Differences between males and females Females Males # of gametes Size of gametes How valuable? MORE SPERM FEWER EGGS SMALLER LARGER MORE! LESS

Intrasexual Selection 1. Females limit male reproductive success. Why? Females EGGS are often, but not always, FEWER and FAR between. 2. This leads to severe what? COMPETITION!!!!!

Intersexual Selection: Mate Choice

Intersexual Selection Seeking PARTNERS with the most ATTRACTIVE attributes Attractive attributes may be: 1. PHYSICAL ex. Peacocks tail 2. BEHAVIOURAL ex. Courtship dances

Sexual Behavior Includes COURTSHIP and the MATING act. Much of the behavior is VISUAL including posture, feather FLUFFING, tail carriage; some of it is AUDITORY, especially in cats, but CHEMICAL communication via PHEROMONES is the clincher.

Sexual Behavior I. Courtship: Purpose of courtship displays: System designed to trap ATTENTION of potential SEXUAL partner All ACTIONS have SPECIFIC meanings.

Sexual Behavior b. Why perform courtship rituals? 1. To find a potential MATE 2. IDENTIFY yourself as the correct SPECIES 3. ATTRACT your potential MATE to you – Close PROXIMITY for MATING 4. AROUSE potential MATES so that they’re physiologically ready. ex. egg in proper position

Sexual Behavior Female Mate Choice: More Prevalent! Why? Females stand to LOSE more than MALES by making BAD choices Females INVEST more ENERGY in each gamete. Females DEVOTE more TIME and ENERGY to their offspring.

Sexual Behavior II. Copulation: Physical act of MATING 1. EXTERNAL Fertilization: Egg and SPERM join OUTSIDE the FEMALE body. Many GAMETES are released into the WATER at the same TIME and LOCATION.

Sexual Behavior EXTERNAL Fertilization: Requires WATER. Why? SPERM must SWIM to the egg Species are either AQUATIC or return to the water for REPRODUCTION

Sexual Behavior 2. INTERNAL Fertilization: Egg and SPERM join inside the FEMALE body Practiced by species that LAY shelled eggs or have a period of internal EMBRYONIC development. Enables animals to reproduce in a TERRESTRIAL environment

Sexual Behavior Internal Fertilization: Males often have a COPULATORY organ to transfer sperm. Examples of Copulatory Organs: 1. Sharks, rays and skates have PELVIC FINS that transfer the sperm into the female. 2. Insects and Mammals have a PENIS 3. Some reptiles and birds have a PENIS 4. MOST reptiles and birds have a single OPENING for the REPRODUCTIVE, excretory and digestive systems called a CLOACA.

Care Giving Behavior III. Epimeletic: MATERNAL Behavior Demonstrated by a FEMALE caring for her YOUNG in the early stages. “SUCCORANT Behavior”: Giving of HELP to a DISTRESSED individual

Care Soliciting Behavior IV. Et-Epimeletic: CARE-seeking behavior Behavioral ACTIVITIES manifested to SOLICIT attention, CARE, or help from other individuals. young RESPONDING to the FEMALE’S care giving. In PUPPIES, this includes TAIL-wagging, LICKING the female's face, and following the female closely. ARISES in situations where an animal is INCAPABLE of adjusting or ADAPTING itself.

Patterns of Growth and Development 1. Altricial: meaning “REQUIRING nourishment“ Found in ORGANISMS which are INCAPABLE of moving around on their own soon after HATCHING or being born. Characteristics: a. IMMOBLE b. LACK HAIR OR DOWN c. CLOSED EYES

Patterns of Growth and Development Examples of ALTRICIAL species: a. HERONS b. Hawks c. WOODPECKERS d. Owls e. RODENTS f. MARSUPIALS g. Cats, Dogs and humans

Patterns of Growth and Development 2. Precocial Species in which the YOUNG are relatively MATURE and MOBILE from the moment of BIRTH or hatching. Chrarcteristics: a. LONGER gestation or incubation period than related altricial species b. SMALLER litters or clutches

Patterns of Growth and Development Examples of PRECOCIAL species: a. HARE b. Guinea Pigs c. SOME Birds